FZ-673 pyrotechnics

[Bret608]

Hi all,

I just finished building a FZ-673 Zonk-alike with the following layout from Tagboard:

http://tagboardeffects.blogspot.com/2014/07/dam-fz-673.html

I've verified parts value and placement. The issue is when I tested it a couple of nights ago (with correct polarity for power/ground observed), it had a weak sound that faded in and lasted about a minute. Then there was a flash of light and a "pop" sound from underneath the trimpot. There was also a slight smoke smell. Also, when I disconnected everything, my battery was actually hot to the touch. I had AC128/125 for Q1/Q3 and an OC47 in Q2. That last one may be fried but need to test it. Looking in the comments in the thread at Tagboard, it looks like John K. may have had a similar issue. I'm not sure I'll risk more of my germanium stash trying to get this working, but in general, what could cause this type of thing? The only thing I noticed in the layout is that the trimmer leg on the left maybe shouldn't have been connected.

Thanks!

Bret

[bluebunny]

Hot battery is a short. Trimmer on fire did the shorting.

Did you make all the cuts indicated on IvIark's layout? Is the 1M really 1M?

[Bret608]

Thank you, Marc! I did make the cuts and yesterday I double-checked there was no continuity across them. I compared with some other MkI/Zonk schematics, and one of the 1Ms is really one 1M. The other is originally 2.2M and D*A*M apparently reduced that to increase the volume output.

I looked at a layout IvIark did for a MkI Bender with a 10k trimmer in a similar place on Q2 (and one on Q3 as well). The difference is he specified clipping off one of the legs. I may try a fixed 8.2k resistor in place of the trimmer and see if that helps.